


Light Me Up

by shamelesstoaster



Category: Undertale (Video Game)
Genre: Awkwardness, Cute, Dating, F/M, Like loads of swearing im sorry, Loss of Virginity, One Night Stands, Original Female Character(s) - Freeform, Romance, Smut, Soul Sex, Soulmate-Identifying Marks, Soulmates, Swearing
Language: English
Status: In-Progress
Published: 2018-01-18
Updated: 2018-01-22
Packaged: 2019-03-06 10:53:11
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 2,855
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13409718
Author URL: https://archiveofourown.org/users/shamelesstoaster/pseuds/shamelesstoaster
Summary: After a one night stand with a monster, Sage, an ordinary human, discovers her soulmate.





	1. Chapter 1

**Author's Note:**

> This was a silly little idea floating around in my head for a while, and I'm not sure where I'll be taking it, so if you guys have any ideas please let me know. I just wanted to do a soulmate thing.

Sunlight slanted through broken shutters in a small, messy room. In the early morning light, a human girl was gradually gaining consciousness. Eyes fluttering open, she gazed up at a ceiling that was not her own, slowly piecing together the events that led her here. 

She shifted, stretching her legs, feeling tender in a few places. Glancing to the side, she gazed upon a skeleton monster sleeping soundly next to her, peaceful and unaware. Well. That definitely happened, then. She turned to face him, careful not to wake him. She was quite proud of herself, actually. Wait till her friends heard she had slept with a monster!

It had been her twenty-first birthday the night before, and she had been determined to find someone to go home with. She had been club-hopping with a few friends, and ended up in a monster-run bar after everyone in her party had found someone to hook up with. Pleasantly drunk and insanely curious, she had been receptive to the attentions of this cute-looking skeleton, and after realising there was a mutual interest born of curiosity and exploration, she agreed to go home with him.

Sage couldn't quite remember everything that went down- the trip from the bar to his room was a blank, and most of her memories of their tryst were pretty blurry- but she knew that she had enjoyed it. There had been magic involved, and this monster had been quite an attentive lover, probably because he had never been with a human before. She remembered him telling her that much in the bar. Well, she hoped he was as satisfied as she was.

What was the protocol for this, though? Was she supposed to just... leave now? Would that be rude? Was she allowed to shower or make breakfast, or would that be weird in a stranger's house? As lame as it sounded, she wished she had researched what to do after a one-night-stand. She knew she was going to make this awkward somehow.

Still staring at the skinless face in front of her, she raised a hand hesitantly to touch the round cheeks. The bone was textured under her fingertips, slightly rough. She couldn't believe she had actually fucked this guy, a literal skeleton, a literal monster! Of all people to have her first casual hook-up with... 

He let out a breath, bony eyelids fluttering open and eyelights focusing on her face. She withdrew her hand, flushing a little. "Good morning..."

"Morning." His eyes roamed over her, taking in her hair, her skin, filled with curiosity. "I'm a little surprised you're still here, to be honest."

"Did you want me to leave now?" She sat up, pulling the sheet over her chest. "I'm sorry, I've never done this before, but I can go..."

"No, no, I just meant... I was expecting you to wake up and discover I'm a monster and freak out." His pleasant, deep voice was tinged with insecurity.

"Well, I didn't, obviously. How..." She bit her lip, looking down at herself self-consciously. "You said this would be your first time with a human. How was it?"

He grinned, his eyelights seeming to twinkle. "You sure gave these old bones a good workout. I enjoyed myself. Did you?"

She nodded vigorously. "Yeah, definitely. I don't remember it all, but I had fun. Thanks for that." She stretched, looking around for her clothes. "Would I be able to use your shower before I leave?"

"Sure, whatever you like. My brother is probably awake now, though, so don't go walking around naked."

"Oh, your brother lives with you?" She reached for her little red dress that was lying on the floor, pulling it over her head. "I hope we didn't bother him last night..."

"Nah, he wouldn't have heard anything. I made sure of it." He sat up, watching her as she tied her purple-grey hair back and stood up, straightening out her skimpy dress. "There should be food in the kitchen, if you wanna stay for that. You don't have to, but the offer is there."

"Thanks, I'll see how I feel after my shower. I'll probably wanna get out of your hair as soon as possible though..." She opened his door, peering into the hallway, then glanced back at him. "Er- I mean-"

"I know what you mean," he snickered, waving her away. "Go have your shower."

She left, tiptoeing down the hall to a door that was obviously for the bathroom. She could hear noises in the kitchen downstairs. Ugh, was she going to have to do the walk of shame in front of his brother? That sucked, but hopefully he wouldn't be awkward about it.

She showered, rubbed her teeth with a little toothpaste, redressed in her now-wrinkled club dress, and sighed at her reflection. Prominent dark circles and patchy dry skin, such A Look. She looked and felt gross, residual alcohol leaving a bad taste in her mouth, but at least she wasn't too hungover besides a fuzzy headache. She'd have bragging rights over her friends now, for sure. 

Right. She'd spent long enough here. Time to go home and stop bugging the guy she was probably never going to see again. She eyed her upper arm, soulmate mark standing out against her fair skin in what looked like a dark shadow. Thank goodness he hadn't been one of those weirdos intent on matching up with her. Did skeleton monsters have marks too? She'd have to ask him, if she ever saw him again.

Nodding at herself in the mirror, she turned on her heel and left the bathroom-

-and ran right into something tall and hard and colourful. Her heart jumped as she grabbed onto whatever it was to avoid falling over.

"OH- A HUMAN!"

Oh. Not something, but someone. She looked up, wide-eyed, at the tall, expressive skeleton. So this was the brother? He looked so different from her hook-up, besides being a skeleton just like him. "Uh, hi? Sorry, I wasn't looking where I was going..." She paused, a strange tingle distracting her train of thought. She looked down, to where he was grasping her upper arm. Right over her soulmark. Which was tingling- no, it was starting to burn now. Frozen, she watched as the skin beneath his hand began to glow orange. What? No, this couldn't be happening right now. It couldn't...

Her hand on his arm bones was tingling too- her eyes widened as something started to glow green. Something in her chest was tightening. She looked up at him, mind blank, not knowing what to do. He seemed to be in the same boat, eyelights fixed on her hand over his arm, and under the colourful shirt that hung off his skeletal frame, his chest seemed to be glowing too.

They stood there, gaping at each other, before he looked over his shoulder and let out a screech. "SANS! COME HERE! YOU'LL NEVER BELIEVE IT!"

She flinched, heart hammering as her chest continued to tighten. Behind him, Sans' door opened and he poked his head out. "What is it, br-" he choked on his words, nearly falling out of the room as he realised what was happening.

Shit. What was she going to do?


	2. Chapter 2

"What... the fuck. What the fuck. What the fuck??" Sans stumbled out of his room, only wearing a hoodie over his otherwise bare bones. "Stop that right now, you can't do that!"

Sage came back down to earth, shaken out of her stupor, and pulled away from the taller skeleton, rubbing her arm. The orange and green wisps of... something... dispersed between them, and the tightness in her chest seemed to lift a little. "I don't- how- what-" Her mind was swimming, trying to process this suddenly messy situation. "You can't be- This can't be happening right now!" She couldn't do this. She had to leave. Panicking, she ducked around the skeleton and hurried down the stairs and out the door, only pausing to shove her feet into a pair of boots by the doorway. 

The sun was too bright. Blinded, she nearly collided with a snazzy red car in the driveway, but righted herself and ran down the street, trying to figure out where she was. How did she even get here last night? How far was she from the bar? The houses all looked the same, and the neighborhood was unfamiliar, but she was pretty sure she could see a landmark that would lead her somewhere close by...

She collided with a body, shrieking as she lost her balance and strong arms grabbed her to prevent her from falling. She blinked at Sans, who straightened her up and stepped back, shoving his hands in his pockets and stepping away. He had pants on now, and fluffy pink slippers and he looked boiling mad, which made for a funny combination. 

"Where the fuck did you come from?" she gasped, backing away from the fuming skeleton.

"Magic. Listen, you have to calm down, ok?" He followed her, hands up in a vaguely placating gesture. "I get it, this is weird and I'm freaking out too, but you can't just run away."

"Watch me." She turned and stalked in the opposite direction, wrapping her arms around herself. This was ridiculous- all she had wanted was a good time, she wasn't looking for a soulmate right now, and he was a monster! And she had slept with his brother! And-

"You forgot your bag."

She started and almost fell over again, staring at Sans, who somehow was standing in front of her. "Godammit- how are you doing that?" She paused, realising he was right. She couldn't leave without her bag.

"It's in my room. Also, you're wearing my brother's shoes- he's gonna want those back." He held out a hand, eyelights soft. "Come on. We'll work this out together."

She huffed, blinking back angry tears. This was not how she wanted to spend the morning after her twenty-first birthday, but it appeared the universe had special plans for her. She couldn't just have a normal, regret-filled morning-after with a wonderful hangover, no. She had to meet her soulmate after fucking his brother. Best get this sorted, then. Reluctantly, she laid her hand in his-

-and gasped as her feet touched a different floor, swaying in his arms. "What the f-"

"YOU'RE BACK!"

She whirled away from Sans and stared up at the taller one- Papyrus, Sans had said? He was staring right back at her, eyelights wide and bright, arms crossed around himself. The insecure expression didn't suit him, what with the bright clothes and loud voice. She felt a tinge of pity for him- it must have looked like she rejected him, and he obviously wasn't taking it well. Fine, she could be nice, just this once. "Uh, yeah, hi. I'm Sage."

"I'M PAPYRUS." He stuck out a hand for her to shake, and she stared at his bare fingers, the ones that had cast orange light on her arm a few minutes ago. This was so surreal...

"Nice to meet you, I guess..." She held her breath and took his hand, hoping the soulmate thing wouldn't make weird magic stuff happen. It didn't. "Look, I know how weird this must seem... I totally understand if you want to pretend it never happened. We can go on with our lives as normal and never have to meet again."

"Hey!" Sans frowned, going to stand next to his brother. "Look, kid, I don't like this either, but you can't just say something like that-"

"Kid?!" Anger was rising, building on top of her headache. She just wanted to go home. "You choose me to satisfy your human kink, fuck me good and proper, and then call me kid in the morning? What the fuck, dude?"

"YOU DID WHAT?" Papyrus turned to him, looking absolutely horrified. "SANS! HOW DARE YOU TREAT MY SOULMATE IN SUCH A DESPICABLE WAY?"

"It's not like that, Paps," he protested. "And I didn't know she was your soulmate!"

"Oh my god..." That word again. She backed away, rubbing her temples. "Look, I don't want a soulmate, ok?"

A pause. She looked back up to see both of them staring at her. Sans' face was set sternly, like he was daring her to repeat herself, while Papyrus looked like he was about to cry.

"YOU DON'T... WANT TO BE MY SOULMATE?" 

"Look, I don't mean to sound rude, but I was hoping to NOT meet my soulmate for a few years, at least." She rubbed her arm where the mark had been, avoiding his cute, sad eyes. "It's not that I don't like you- I mean I don't even know you so I can't really-"

"WE SHOULD GET TO KNOW EACH OTHER, THEN." His voice was pleading, and she could feel herself being worn down. Damn bleeding heart.

How could she tell this guy that she didn't want to get to know him? She'd sound like an asshole. She knew that obligation was a terrible reason to do anything, but he was so cute and sad and maybe she'd end up liking him, after all.

"Maybe. Look, I'm a busy person, but maybe I can work something out." 

He smiled, straightening up, confidence visibly returning. "GOOD! WONDERFUL! PERHAPS WE SHOULD HAVE CELEBRATION SPAGHETTI FOR BREAKFAST, TO CELEBRATE THIS JOYOUS DAY!"

Spaghetti... for breakfast? The very thought made her ill- or was that the hangover? Ugh, she just wanted to go home. "Uh, can we, like, postpone that or something? I gotta get home, I'm sorry. Another time." She turned to Sans. "My bag?"

"Oh, right." Before she had time to blink, he had vanished from before her eyes. And then before she had time to react, he was back, holding out her handbag and shoes. "Here. You guys should exchange numbers or something."

"OF COURSE!" Papyrus clasped his hands together. "HUMAN, HERE IS MY PHONE NUMBER-"

"Wait, wait." She scrambled to pull out her phone and brought up her contacts. "Ok, go."

He gave it to her, and she promised to text him. Changing shoes, she stepped away. "Ok, well, I should get home now..."

"Oh, here, let me take you somewhere you know." Sans held out a hand again, and she eyed him shrewdly. 

"You're gonna teleport me somewhere?"

"Yeah, I did it this morning, didn't I? And last night." He raised a brow bone. "Don't you trust me?"

"Of course not," she grumbles, but took his hand anyway. "What the hell. Do you know the bus stop near the McDonald's?"

"Yep! Hold on tight."

One moment, she was standing in their living room. The next, she was exactly where she had asked to be. She righted herself quickly and backed away, crossing her arms. "Thanks. Now, uh, what's the likelihood of being able to pretend this never happened and getting on with my life without ever seeing you again?"

He regarded her sternly, eyes narrowed. "Ok, look. What happened is weird, but if you break my brother's heart I will not hesitate to fuck you up. Or at the very least, annoy you until you agree to at least give him a chance."

"I thought you didn't want him to be with me?"

"I'm not happy about it, no. But soulmates are a huge thing, and Papyrus is a sweet, caring monster who will definitely treat you right. I just..." He huffed in frustration, crossing his arms. "He's innocent, and I've been taking care of him for so long, and I hate the idea of anyone corrupting him."

"Corrupting- you think I'll- what kind of corrupting?" She scowled, pointing at him. "You think I'm a slut or something? Just because I went home with you last night? Ok, buddy, listen up. One, that was my first one-night-stand ever. Two, even if it wasn't, you have no right to slut-shame me. And three, your brother is an adult and can make his own decisions. Back off." Oh boy, now she sounded like she was arguing for the right to be his soulmate. She cringed at herself, wishing everything would just go away.

"Look, I just want what's best for him, ok?" He shrugged, looking a little lost after her outburst. "I know I can't make these decisions for him, so I'm asking you to think about this before you walk away from it. Please. For everyone's sake."

"Fine." She stalked over to the seat at the bus stop, sitting down and turning away from him. "I'll consider it. Now go away."

She heard a shuffle of feet, then nothing. Peeking back to see an empty sidewalk, she pulled out her phone and stared down at her new contact, reaching idly to scratch at her arm. Looks like she needed to think about her life a little bit. But that could wait- she needed to get home and nap a little before work. Maybe throw out her party dresses and make a sacred vow to never seek out casual sex again. She snorted, tears pricking her eyes despite her best efforts to remind unaffected.

"Stupid fucking soulmates..."

**Notes for the Chapter:**

> I don't know what I'm doing.
> 
> I'll be introducing more monsters soon.

**Author's Note:**

> What even is this.
> 
> All I know is it's gonna be cute and awkward and smutty, eventually. So uh, enjoy I guess?


End file.
